Apparatus for developing latent electrographic images with liquid ink

ABSTRACT

An electrographic developer is disclosed which includes an ink pervious development electrode structure having a development surface over which an electrographic recording web bearing latent electric charge images to be developed is disposed. Liquid ink is forced through the ink pervious electrode structure against the image bearing surface of the recording web for developing the latent charge image pattern. The development electrode can take the form of a plate, a roller or a continuous belt. In the case of the continuous belt or roller, ink is forced through the ink pervious electrode structure from the inside and the recording web is pressed into engagement with the outer surface of the electrode structure.

United States Patent [7 2] Inventor Raymond L. Levy Santa Clara, Calif.[21] Appl. No. 858,044 [22] Filed Sept. 15, 1969 [45] Patented Nov. 9,1971 [73] Assignee Varian Associates Palo Alto, Calif.

[54] APPARATUS FOR DEVELOPING LATENT ELECTROGRAPHIC IMAGES WITH LIQUIDINK 6 Claims, 4 Drawing Figs.

[52] U.S. Cl 118/637, 118/638,117/17.5 [51] Int. Cl 603g 13/00 [50]Field of Search 118/602, 638, 637, 410, 637 LX; 117/37, 934, 93.4 A,93.41

[56] References Cited UNITED STATES PATENTS 1,928,235 9/1933 Taylor118/637 L X 2,431,041 11/1947 l-lassler 118/637 L X 3,202,072 8/1965Limberger. 118/637 L X 3,284,224 11/1966 Lehmann 118/637 L X 3,177,7934/1965 Stewart 118/637 L 3,249,088 5/1966 Ostensen 118/637 Crawford, T.M., Developing Electrostatic Charge Patterns, IBM Technical DisclosureBulletin; Vol. 8, No. 4, Sept, 1965, Page 527.

Primary Examiner-Mervin Stein Assistant Examiner- Leo MillsteinAttorneys-Leon F. Herbert and Gerald L. Moore ABSTRACT: Anelectrographic developer is disclosed which includes an ink perviousdevelopment electrode structure having a development surface over whichan electrographic recording web bearing latent electric charge images tobe developed is disposed. Liquid ink is forced through the ink perviouselectrode structure against the image bearing surface of the recordingweb for developing the latent charge image pattern. The developmentelectrode can take the form of a plate, a roller or a continuous belt.In the case of the continuous belt or roller, ink is forced through theink pervious electrode structure from the inside and the recording webis pressed into engagement with the outer surface of the electrodestructure.

PATENTEB NUV 9197i 3, 1 ,5 7

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RAYMOND L. LEVY we' W ATTORNEY PATENTEIJNUV 9mm 3518,56?

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RAYMOND L. LEVY \amqw ATTORNEY APPARATUS FOR DEVELOPING LATENTELECTROGRAPHIC IMAGES WITH LIQUID INK DESCRIPTION OF THE PRIOR ARTI-Ieretofore, development electrodes for developing electrographicimages with liquid ink have employed a porous development electrode tobe saturated with electrographic ink for carrying the ink to the chargeretentive surface of the recording web to be developed. In the case of acontinuous printer, the porous development electrode took the form of adrum having a lower portion thereof immersed in a reservoir ofelectrographic ink such that as the drum rotated it picked up additionalink to supply the ink lost to the recording web. The problem with thisprior art electrographic developing apparatus was that at relativelyhigh printing and developing speeds, the rate of depletion of pigmentedtoner particles from the liquid carrier was greater than the normalreplacement by particle migration in the fluid at the surface, such thatthe electrographic charge images were not sufficiently developed. Anexample of this prior art porous development electrode inker isdisclosed in US. Pat. No. 3,096,198 issued July 2, 1963.

Others, have proposed electrographic inkers wherein an ink absorbentpad, as of cotton, felt or fiberglass, was impregnated or supplied withink from a reservoir under pressure. The pad was caused to contact thecharge image bearing surface of the recording web for developing same.In one such prior proposal the recording web to be developed wasdisposed between a roller and an absorbent pad, there being a geararrangement connected to the roller for causing the supply of inksupplied to the absorbent pad to vary in accordance with the rotationalspeed of the roller. However, use of such a nonconductive absorbent padis not suitable for development of a relatively large areaelectrographic images, such as encountered in electrophotography, sincethe proper development of such large area images requires the provisionof a development electrode adjacent the charge image bearing surface ofthe recording web. Moreover, the use of the absorbent pad inker provideda relatively small contact area between the pad and the recording webwhich tends to substantially reduce the available development time andtherefore substantially limits the speed at which electrographic imagescan be properly developed due to the relatively low mobility of thepigment particles in the ink.

SUMMARY OF THE PRESENT INVENTION The principal object of the presentinvention is the provi sion of an improved developer for developinglatent electrographic images with liquid electroscopic ink.

One feature of the present invention is the provision, in anelectrographic inker, of an ink pervious conductive developmentelectrode structure and means for forcing electroscopic ink through theink pervious development electrode structure onto the image bearingsurface of an electrographic recording web to be developed, wherebyrelatively large area develop- 7 ment is possible at relatively highdevelopment speeds.

Another feature of the present invention is the same as the precedingfeature wherein the ink pervious development electrode structure isformed into a closed path such as that provided by a continuous belt ordrum and wherein an arcuate inking trough structure is disposed insidethe continuous belt or drum for forcing the liquid electroscopic inkthrough the ink pervious development electrode structure to therecording web partially wrapped around the outside of the developmentelectrode structure, whereby ink is supplied simultaneously to arelative large area of the recording web to be developed.

Another feature of the present invention is the same as the precedingfeature wherein ink is fed to the inking trough by a hollow axle onwhich the ink pervious drum is rotatable.

Another feature of the present invention is the same as any one or moreof the preceding features wherein an elastic belt is at least partiallywrapped around and movable with a closed path ink pervious developmentelectrode structure for pressing the recording web into engagement withthe movable development electrode structure.

Other features and advantages of the present invention will becomeapparent upon a perusal of the following specification taken inconnection with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exploded schematicperspective view, partially broken away, depicting an electrographicinker incorporating an ink pervious conductive pad,

FIG. 2 is a side cross-sectional view of an electrographic inkerincorporating an ink pervious conductive roller,

FIG. 3 is a sectional view of the structure of FIG. 2 taken along line3-3 in the direction of the arrows, and

FIG. 4 is a schematic line diagram depicting an alternativeelectrographic inker incorporating an ink pervious conductive belt.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, thereis shown an electrographic inker 1 for developing relatively large areaelectrographic images, such as those obtained by electrophotography, andincorporating features of the present invention. Electrographic inker 1includes an ink pervious development electrode structure 2 having adevelopment surface 3 over which is disposed the charge retentivesurface of an electrographic recording web 4 to be developed.Electroscopic ink is supplied to the development electrode structure 2from a reservoir 5 disposed below the level of the development electrode2 via an ink return line 6 and a pump 7. The ink pervious developmentelectrode structure 2 includes an ink pervious plate 8, as of 0.046 inchthick porous stainless steel. A suitable porous stainless steel materialis commercially available under the trade name Felt Metal FM-l 23-125from Huyck Metals Company, 45 Woodmont Road, Milford, Connecticut. Suchink pervious stainless steel plate is porous with the average pore sizefalling within the range of to microns and is approximately 65 percentdense.

The ink pervious plate 8 closes off the top of a rectangular chamber 9into which is fed the electroscopic ink via pump 7 and line 6 from thereservoir 5. The output pressure of the pump 7 is adjusted such thatthere is a continuous flow of ink through the ink pervious plate 8against the charge-bearing surface of the recording web 4 for developingsame. The excess ink flows over the side edges of the developmentelectrode structure 2 and is caught by the reservoir 5 forrecirculation. A backup plate electrode structure 11 is disposedadjacent the conductive side of the recording web 4 and a source ofpotential 12 is connected between the backup plate 11 and thedevelopment electrode structure 2 for applying a suitable developmentpotential across the recording web 4 during development thereof.

. In FIG. 1 the view is exploded for the sake of explanation. However,in use, the recording web 4 would be placed in nominal contact with thedevelopment surface 3 of the development electrode structure 2 and thebackup plate 11 would be placed into nominal contact with the conductivesurface of the electrographic recording web 4. In this manner, theelectroscopic ink is applied only to the image-bearing surface of therecording web 4 and an adequate supply of electroscopic ink iscontinuously supplied to the image for developing same in a relativelyshort development time span. The use of the conductive developmentelectrode structure 2 assures uniform development and proper gray scaletonal characteristics to the resultant print when relatively large areacharge images are to be developed, such as those encountered inelectrophotography.

Referring now to FIGS. 2 and 3, there is shown a relatively high speedcontinuous electrographic developer 14 incorporating features of thepresent invention. The developer 14 includes a drum-shaped developmentelectrode structure 15. The cylindrical wall of the developmentelectrode structure 15 is made of the ink pervious conductive material,such as that described above for plate 8 of the development electrodes 2of F IG. 1. The drum is carried upon a centrally disposed axle 16 whichin turn is fixedly secured, at its ends, to a metallic housing 17 vialock nuts 18. The axle 16 includes an axially offset portion 19 disposedimmediately adjacent the inside surface of the drum 15 and including anaxially directed recessed portion 21 to define an inking trough.

An electroscopic ink distribution manifold 22 is disposed inside thedrum 15 and includes a tubular portion23 defining an ink inlet tubepassing axially through the hollow axle 16 to the output of an ink pump24 which in turn is connected to a reservoir 25, disposed below theinking drum 15, via pump inlet conduit 26. A plurality of feed conduits27 branch off from the main conduit 23 and are connected to nipples 28passing through the bottom of the inking trough 21 at a plurality ofaxially spaced positions 29 for feeding electroscopic ink from the pumpvia conduit 23 and feed lines 27 into the inking trough 21.

A curved skirt portion 31, of cylindrical section, is affixed to oneside of the inking trough 21 and extends in the direction of rotation ofthe drum along the inside surface of the drum and conforming to theinside surface of the drum. The spacing between the skirt 31 and theinside surface of the drum 15 is made relatively small to trapelectroscopic ink in the space between the skirt 31 and the drum 15 withsubstantial hydrostatic pressure derived from the inking trough 21. Inthis manner, ink is forced due to the hydrostatic pressure through theink pervious drum over a substantial arcuate section of the drum, as of90 of arc, to provide a relatively large development area, more fullydescribed below.

The drum 15 is supported from axle 16 via electrically insulativebearings 32, as of Teflon. A development potential is applied to thedrum 15 from a source of potential 33 via lead 34 and wiper blade 35bearing in slidable engagement on a hub portion 36 of the drum 15. Thedrum 15 is rotatably driven around the axle 16 from a motor, not shown,via a chain driven sprocket 37 fixed to the opposite hub 36' of the drum15.

A plurality of elastic bands or belts 38 are carried in V grooves in theperiphery of wheels 39, 40, and 41 carried upon axles 42, 43,and 44respectively. The elastic bands 38, as of neoprene rubber, are arrangedto ride in elastic bearing engagement with a substantial arcuate sectionof the periphery of the drum 15, indicated at 45 in FIG. 2. Drive wheels39 are rotationally driven via a chain driven sprocket 46 pinned to axle42. The drive wheels 39 are driven at such a speed that the elasticbands 38 move at the same speed as the periphery of the rotating drum15.

An electrographic recording web 4 to be developed is slipped intoposition between the elastic bands 38 and the periphery of the drum 15with the charge image-bearing surface of the recording web 4 facing thedrum 15. The recording web 4 is partially wrapped around the drum 15 viathe provision of the elastic bands 38 and the rotation of the drum 15such that the charge image on the recording web is exposed toelectroscopic ink flowing through the drum 15 over substantially theentire arcuate extent of the skirt 31 and trough 21, roughly indicatedby numeral 45.

Drive 42, and idler shafts 43 and 44 for the belt drive wheels 39, andidler wheels 40 and 41 are carried at their ends from the housing 17 viaretaining rings 48. A second sprocket 49 is affixed to drive shaft 42and a chain schematically indicated at 50, is fixed to sprocket 49 andconnected to the pump 24 for causing the flow through the pump to varyin accordance with the rotational speed ofthe drum 15. In a typicalexample, 0.23 gallons per minute of electroscopic ink is fed through thepump 24 and inking trough 21 for developing electrographic recordingwebs carried around the drum 15.

Wipers 51 are disposed around each of the elastic belts 38 for wipingthe ink off the bands and returning the ink to the reservoir 25.

A comb-shaped structure 52 is disposed with its fingers riding inslidable engagement with the surface of the rotating drum 15 opposite,or near to, the end of the skirt 3] for peeling the developedelectrographic recording web from the drum 15 and feeding the developedweb through a pair of squeegee rollers 53 for squeegeeing ink from therecording web. Thence, the developed web is fed through a dryingsection, not shown, wherein the web is dried by an airblower.

Referring now to FIG. 4, there is shown, in schematic line diagram form,an electrographic inker 61 incorporating alter native features of thepresent invention. inker 61 is substantially the same as that describedabove with regard to FIGS. 2 and 3 with the exception that instead ofusing a cylindrical inking drum 15 a continuous sheet metal band 62 ofporous metal, as of 0.010 inch thick stainless steel is employed. Band62 is formed into an oblong path having a relatively large radius ofcurvature for the arcuate section 45 to be contacted with the recordingweb 4 for development thereof. in this manner, the volume of the inkingapparatus that has to be devoted to the development electrode structureis substantially reduced compared to the use of a cylindrical or a drumshaped development electrode 15, as shown in FIGS. 2 and 3. Thecontinuous belt electrode 62 is rotationally driven by a frictionaldrive roller 63 disposed at one end of the elongated closed loop of thebelt and opposite from an idler roller 64 disposed at the opposite endof theoblong loop of the belt 62.

Since many changes could be made in the above construction and manyapparently widely different embodiments of this invention could be madewithout departing from the scope thereof, it is intended that all mattercontained in the above description or shown in the accompanying drawingsshall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. An apparatus employing liquid ink having a suspension of tonerparticles therein for developing the charge image on the chargeretentive surface ofa moving recording medium, com prising thecombination:

a rotatable drum developing electrode made ofink pervious conductivematerial the outside surface of which is adapted to engage the chargeretentive surface of the moving recording medium as the drum rotates;

liquid ink feed trough positioned proximate the inside sur' face of thedrum development electrode and displaced slightly from top dead centerin the direction of rotation for preventing ink from flowing onto theback of the recording medium;

hollow axle means for supporting the rotatable drum and for distributingfresh liquid ink to the feed trough; and

hydrostatic pressure means for forcing the ink from the feed troughthrough the porous drum development electrode and onto the chargeretentive surface of the recording medium to continuously replenish thetoner particles as the development proceeds and toner particles aredepleted from the ink.

2. The apparatus of claim 1, wherein the feed trough includes a skirtstructure extending in an are around the inside surface of the drum inthe direction of rotation for establishing a hydrostatic pressure headon the liquid ink contained between the skirt and the drum.

3. An apparatus for developing the charge image on the charge retentivesurface of a moving recording medium with liquid ink-containingparticles of toners suspended therein, comprising the combination:

a development electrode which is pervious to the liquid ink and has anupper surface adapted to engage the charge retentive surface of therecording medium;

liquid ink feed trough positioned proximate the underside of thedevelopment electrode for supplying liquid ink against the undersurfaceof the development electrode;

a skirt extending from the feed trough along the underside of thedevelopment electrode and proximate to the development electrodedefining a liquid ink distribution channel; and

5. The apparatus of claim 4, wherein the feed trough is displacedslightly from top dead center of the loop development electrode in thedirection of rotation for preventing liquid ink from flowing onto theback of the recording medium.

6. The apparatus of claim 4, wherein the area of engagement between therecording medium and the outside surface of the loop developmentelectrode is at least partially coextensive with the area of thedistribution channel along the inside surface of the loop developmentelectrode.

1. An apparatus employing lIquid ink having a suspension of tonerparticles therein for developing the charge image on the chargeretentive surface of a moving recording medium, comprising thecombination: a rotatable drum developing electrode made of ink perviousconductive material the outside surface of which is adapted to engagethe charge retentive surface of the moving recording medium as the drumrotates; liquid ink feed trough positioned proximate the inside surfaceof the drum development electrode and displaced slightly from top deadcenter in the direction of rotation for preventing ink from flowing ontothe back of the recording medium; hollow axle means for supporting therotatable drum and for distributing fresh liquid ink to the feed trough;and hydrostatic pressure means for forcing the ink from the feed troughthrough the porous drum development electrode and onto the chargeretentive surface of the recording medium to continuously replenish thetoner particles as the development proceeds and toner particles aredepleted from the ink.
 2. The apparatus of claim 1, wherein the feedtrough includes a skirt structure extending in an arc around the insidesurface of the drum in the direction of rotation for establishing ahydrostatic pressure head on the liquid ink contained between the skirtand the drum.
 3. An apparatus for developing the charge image on thecharge retentive surface of a moving recording medium with liquidink-containing particles of toners suspended therein, comprising thecombination: a development electrode which is pervious to the liquid inkand has an upper surface adapted to engage the charge retentive surfaceof the recording medium; liquid ink feed trough positioned proximate theunderside of the development electrode for supplying liquid ink againstthe undersurface of the development electrode; a skirt extending fromthe feed trough along the underside of the development electrode andproximate to the development electrode defining a liquid inkdistribution channel; and pump means for forcing the liquid ink from thefeed trough into the ink distribution chamber between the skirt and thedevelopment electrode and through the development electrode and onto thecharge retentive surface of the recording medium.
 4. The apparatus ofclaim 3, wherein the development electrode is formed in a rotatableclosed loop the outside surface of which engages the charge retentivesurface of the recording medium and the inside surface of which isdisposed toward the feed trough and the skirt.
 5. The apparatus of claim4, wherein the feed trough is displaced slightly from top dead center ofthe loop development electrode in the direction of rotation forpreventing liquid ink from flowing onto the back of the recordingmedium.
 6. The apparatus of claim 4, wherein the area of engagementbetween the recording medium and the outside surface of the loopdevelopment electrode is at least partially coextensive with the area ofthe distribution channel along the inside surface of the loopdevelopment electrode.